Particle Detection on Patterning Devices with Arbitrary Patterns

Abstract

A detection system for detecting particle contamination in a lithographic apparatus includes an illumination system that directs a radiation beam onto a section of a surface of a patterning device to generate at least first and second components of patterned radiation. A first detector is configured to detect the first component. A filter is configured to adaptively change the second component based on the detected first component, and a second detector is configured to detect the filtered second component. An imaging device generates an image corresponding to the detected second filtered component, and the image indicates an approximate location of a particle on the surface of the patterning device.

1 . A system for detecting particle contamination of a patterning device in a lithographic apparatus, comprising:
 an illumination system configured to direct a radiation beam onto a section of a surface of the patterning device to generate at least first and second components of patterned radiation;   a first detector configured to detect the first component;   a filter configured to adaptively change the second component, the change being based on the detected first component;   a second detector configured to detect the filtered second component; and   an imaging device configured to generate an image corresponding to the detected second filtered component,   wherein the image is configured to indicate an approximate location of particle contamination on the surface of the patterning device.   
   
   
       2 . The system of  claim 1 , wherein the filter comprises a liquid crystal device (LCD) array. 
   
   
       3 . The system of  claim 1 , wherein the filter comprises a first LCD array of pixels and a second LCD array of pixels. 
   
   
       4 . The system of  claim 3 , wherein each pixel of the first LCD array is aligned with a corresponding pixel of the second LCD array. 
   
   
       5 . The system of  claim 3 , wherein each pixel of the first LCD array is offset from a corresponding pixel of the second LCD array. 
   
   
       6 . The system of  claim 3 , further comprising:
 an imaging device configured to generate an image corresponding to the detected first component,   wherein the filter is configured to adaptively filter the second component based on the generated image.   
   
   
       7 . The system of  claim 6 , wherein the generated image corresponds to an image of a pattern imparted onto the first component by the section of the patterning device. 
   
   
       8 . The system of  claim 7 , wherein the section of the patterning device is free of particles. 
   
   
       9 . A lithographic apparatus, comprising:
 a structure configured to receive a patterning device located in a vacuum environment, the patterning device being configured to pattern a beam of radiation;   a projection system configured to project the patterned beam onto a target portion of a substrate within the vacuum environment; and   a detection system configured to detect a respective particle contamination on a surface of the patterning device, comprising:
 an illumination system configured to direct a radiation beam onto a section of a surface of a patterning device to generate at least first and second components of patterned radiation; 
 a first detector configured to detect the first component; 
 a filter configured to adaptively change the second component, the change being based on the detected first component; 
 a second detector configured to detect the filtered second component; and 
 an imaging device configured to generate an image corresponding to the detected second filtered component, 
 wherein the image is configured to indicate an approximate location of particle contamination on the surface of the patterning device. 
   
   
   
       10 . The lithographic apparatus of  claim 9 , wherein the filter comprises a liquid crystal device (LCD) array. 
   
   
       11 . The lithographic apparatus of  claim 9 , wherein the filter comprises a first LCD array of pixels and a second LCD array of pixels. 
   
   
       12 . The lithographic apparatus of  claim 9 , wherein each pixel of the first LCD array is aligned with a corresponding pixel of the second LCD array. 
   
   
       13 . The lithographic apparatus of  claim 11 , wherein each pixel of the first LCD array is offset from a corresponding pixel of the second LCD array. 
   
   
       14 . The lithographic apparatus of  claim 11 , further comprising:
 an imaging device configured to generate an image corresponding to the detected first component,   wherein the filter is configured to adaptively filter the second component based on the generated image.   
   
   
       15 . The lithographic apparatus of  claim 14 , wherein the generated image corresponds to an image of a pattern imparted onto the first component by the section of the patterning device. 
   
   
       16 . The lithographic apparatus of  claim 15 , wherein the section of the patterning device is free of particles. 
   
   
       17 . A method for detecting particle contamination on a patterning device in a lithographic apparatus, comprising:
 (a) illuminating a section of a surface of a patterning device with a beam of radiation to generate at least first and second components of patterned radiation;   (b) measuring an intensity of the first component;   (c) filtering the second component based on at least the measured intensity of the first component;   (d) generating an image corresponding to the filtered second component based on at least the measured intensity of the second component; and   (e) identifying particle contamination on the illuminated section of the surface of the patterning device based on an inspection of the generated image.   
   
   
       18 . The method of  claim 17 , wherein step (d) comprises:
 measuring an intensity of the filtered second component.   
   
   
       19 . The method of  claim 17 , wherein step (b) comprises:
 generating an image of a pattern imparted onto the first component by the section of the surface of the patterning device based on the measured intensity of the first component.   
   
   
       20 . The method of  claim 17 , wherein step (a) comprises:
 illuminating a section of a surface of a particulate-free patterning device with a beam of radiation to generate patterned radiation.   
   
   
       21 . The method of  claim 17 , wherein step (c) comprises:
 filtering out the measured intensity of the first component from the second component to generate a filtered radiation beam.   
   
   
       22 . The method of  claim 21 , wherein step (e) comprises:
 identifying one or more sub-resolved images in the generated pattern to detect if there is any of the particle contamination.   
   
   
       23 . The method of  claim 21 , wherein step (e) further comprises:
 identifying a location of any respective particle within the section of the surface of the patterning device based on a location of a sub-resolved image in the generated pattern.   
   
   
       24 . The method of  claim 17 , further comprising:
 (f) repeating steps (a) through (e) for a different section of the surface of the patterning device.